1. Field of the Invention
The present invention relates to a steering control apparatus for imparting a return torque for returning a steering system to its neutral position.
2. Related Background of the Invention
In automobiles, as friction of a steering system increases or as tire returnability becomes weaker, the friction of the steering system and the tire return force balance each other out up to a larger steer angle, so as to degrade steering wheel returnability. Particularly, where the steering system is equipped with an electric power steering system, the steering wheel returnability becomes more degraded because of friction between gears for transmitting a torque generated by a motor, inertia of the motor, and so on. In order to enhance the steering wheel returnability, some electric power steering systems are configured to impart a return torque for returning the steering wheel to the neutral position when the driver intends to return the steering wheel (Japanese Patent No. 3082483). For making a return decision on whether the driver intends to return the turned steering wheel to the neutral position, a direction of steering torque is compared with a direction of steering angular velocity and it is determined that the driver intends to return the steering wheel, if these two directions are different.